Flat Crystalline Structures of Poly(3-hexylthiophene) and Poly

Dec 5, 2016 - Anisotropic accumulation of grafted coily PEG blocks on the opposite surfaces of P3HT half-rings having extended backbones reflected scr...
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Scrolled/Flat Crystalline Structures of Poly(3-hexylthiophene) and Poly(ethylene glycol) Block Copolymers Subsuming Unseeded HalfRing-Like and Seeded Cubic, Epitaxial, and Fibrillar Crystals Samira Agbolaghi,†,‡ Sahar Zenoozi,†,‡ Zahra Hosseini,†,‡ and Farhang Abbasi*,†,‡ †

Institute of Polymeric Materials and ‡Faculty of Polymer Engineering, Sahand University of Technology, 5331711111 Tabriz, Iran S Supporting Information *

ABSTRACT: Three distinct types of poly(3-hexylthiophene) (P3HT)-based crystals were developed using unseeded and seeded protocols. First, unseeded flat fibrillar and scrolled halfring-like crystals were prepared by isothermal crystallization of homo-P3HT and P3HT-b-poly(ethylene glycol) (PEG) block copolymers. Anisotropic accumulation of grafted coily PEG blocks on the opposite surfaces of P3HT half-rings having extended backbones reflected scrolling, and their subsequent crystallization also further intensified this scrolling. The PEGs assembled into lamellae on both sides of P3HT half-rings with dissimilar crystalline features, i.e., the outer PEG lamella was thicker (17.4 nm) and wider (23.1 nm) compared to the inner one (15.0 and 18.1 nm). Furthermore, the crystallinity of PEG coily blocks accumulated on the P3HT crystals did not change the extended state of P3HT backbones (17.5 nm) and also the thickness of half-rings (11.0 nm). Second, with seeding homogeneous P3HT7000-b-PEG5000 solution using homo-PEG5000 tiny crystals, the cubic PEG single crystals were sandwiched between grafted regioregular P3HT chains (>99%). The appearance of (020)P3HT and (100)P3HT spots for tethered P3HTs beside (120)PEG prisms demonstrated flat-on orderly tethered P3HT backbones on the PEG single crystalline substrate. Via conjunction between block copolymer and homopolymer single crystals in channel (PEG)/wire (P3HT-covered PEG)/channel (PEG) epitaxials, the P3HT rigid brushes were found to be extended (17.35 nm) on lamellar PEG substrate (6.15 nm). Third, when homogenized P3HT7000-b-PEG5000 solutions were seeded by homoP3HT7000 tiny crystals, the edge-on orientated fibrillar P3HT single crystals were acquired. Although the thickness (20−22 nm) and length (60−63 μm) of P3HT7000-b-PEG5000 fibrillar single crystals resembled those of homo-P3HT7000 ones, their backbone lamination in the c axis were significantly different (2 versus 21); because the P3HT backbones were not capable of laminating from the coily block sides.

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INTRODUCTION Polymer single crystals with their uniform thicknesses, dimensions, and homogeneous chemical and physical properties1−5 are a special kind of ultrathin films.6,7 The programmable nanoparticle assembling,8 free-standing substrates,9 recyclable catalyst supports,10−14 templating and deposition of nanoparticles,15−17 semiconductor microelectronics,18,19 ultrathin films,20 and medical delivery systems21−23 were some of the potential applications reported for the single crystals. On the other hand, reaching the conjugated polymer-based single crystals was more challenging compared to the oligomers24 and small molecules.25 Conductive single crystals reflect the outstanding intrinsic charge transport properties due to their high chemical purity.25−29 Owing to the perfect order of molecules, the absence of grain boundaries, and a minimal number of charge traps, the organic single crystals could be applied in flexible and inexpensive applications like flexible displays, radio frequency identification devices, smart cards, memory, solar cells, and sensors.30−34 Good alignment of single crystal organic nanowires in the high-performance devices reduces the parasitic leakage paths and controls the azimuthal © XXXX American Chemical Society

orientation of the nanowires for optimal charge transport.25,35,36 Among the conductive polymers, poly(3-hexylthiophene) (P3HT) could assemble into the fibrillar crystals to facilitate the efficient hole transport in field-effect transistors (FETs)37 and solar cells.38,39 Understanding the P3HT crystallization and controlling the crystal dimension are important to improve device performance as well as to design new semiconductive polymers with high charge mobility.40−42 In comparison to two-dimensional (2D) lamellar crystallization of conventional polymers such as polyethylene (PE), the P3HT develops one-dimensional (1D) crystals via the π−π interactions among the polymer backbones.30,43−45 Besides all conjugated polymer single crystals, recently some sandwiched conductive-dielectric-conductive single crystals have been introduced, which could have the applicability in micro/nano electronic devices. Wang et al.46 utilized a nonisothermal solution crystallization technique to prepare Received: October 23, 2016 Revised: November 23, 2016

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Figure 1. Color of solution environment before (top, left) and after (top, right) development of P3HT-based crystalline structures; chemical structures of the synthesized P3HT-b-PEG block copolymers represented in orange panel (bottom, left); four different structures developed during crystallization depicted in red panel (bottom, right). P3HT7000-b-PEG5000) was dissolved in amyl acetate with the concentration of 0.01 wt % and kept at the dissolution temperature for 30 min. In unseeded isothermal crystallization of homo-P3HT7000 and P3HT7000-b-PEG5000 polymers, the vials containing prepared solutions were then maintained for 24 at respective crystallization temperature (i.e., 10, 30, and 50 °C) as reported in Figure S5(a). The nanofibers and half-ring-like crystals were developed with this method. For seeding P3HT7000-b-PEG5000 solution with the seeds of homoPEG5000, a two-step process was used. The solution of P3HT7000-bPEG5000 in amyl acetate was homogenized at 100 °C for 30 min. The vial was subsequently kept at 30 °C for 3 min. Simultaneously, the solution of homo-PEG5000 in amyl acetate was homogenized at 70 °C for 30 min and then was switched to 40 °C for 10 min to prepare the desired seeds. The prepared seeds were transferred to the vial of first step, which was kept at 30 °C for 3 min and the crystallization continued for 24 h at the same temperature (30 °C). Figure S5(b) schematically represents this procedure. The consequence of this seeding approach was the cubic PEG single crystals with the regioregular P3HT grafted chains on the substrate surface. In a similar protocol, the seeds of homo-P3HT 7000 were added to the homogenized P3HT7000-b-PEG5000 solution. The scheme of this methodology is reported in Figure S5(c) with more details, through which the fibrillar P3HT single crystals were resulted. The channel (PEG)/wire (P3HT-covered PEG)/channel (PEG) single crystals were developed using the large pregrown single crystals as the seeds. As shown in Figure S5(d), the first channel or, in better words, the core of epitaxial structure was grown according to abovementioned process but with a crystallization duration time of 8 h. The resulted cubic homo-PEG5000 single crystals were transferred as the seeds to P3HT7000-b-PEG5000 solution, which was previously homogenized at 100 °C for 30 min and was kept at 30 °C for 3 min. Subsequently, the crystallization continued for 8 h at the same temperature to develop the second channel of epitaxial structure. The channel-wire single crystals were then employed as the seeds to induce the crystallization in the third step. Therefore, these crystals were added to the homogeneous solution of homo-PEG5000, which was previously dissolved at 70 °C for 30 min and kept at 30 °C for 3 min. Finally, the crystallization continued for 3 h to complete this step. The ultraviolet-visible (UV−vis) absorption spectra were recorded by a Lambda 750 UV−vis spectrometer using the ultimate solutions containing fibrillar, half-ring, cubic, and epitaxial developed crystalline structures in amyl acetate. In details, the spectra recording was

the single crystals of poly(3-butylthiophene) (P3BT)-b-PE diblock copolymers, in which the P3BT blocks were excluded to both top and bottom surfaces of the PE crystals. Furthermore, the conductive polyaniline (PANI) nanorods were developed via the growth of single crystals of PANI and PEG block copolymers.47−49 In these systems, two different surface morphologies, i.e., matrix-dispersed and disperseddispersed morphologies were detected based on the diameter dispersity of PANI nanofibers and distinct molecular weights of crystalline PEG substrates.47 In this work, the crystalline behavior of P3HT chains were scrutinized in distinct roles including unseeded P3HT-b-PEG scrolled half-ring-like crystals as well as flat fibrillar nanofibers and single crystals from P3HT-based homopolymers and conductive-dielectric block copolymers. In particular, the P3HT backbones were tethered with a flat-on orientation as conductive regioregular brushes on the PEG single crystals. In a forward step, the features of grafted P3HT brushes were investigated through developing the channel (PEG)/wire (P3HT-covered PEG)/channel (PEG) epitaxial single crystals.

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EXPERIMENTAL SECTION

Syntheses. Highly regioregular P3HTs (>99%) with the molecular weight (Mn) of 7 kDa and the corresponding block copolymers with PEG (Mn = 5 kDa) were synthesized using Grignard metathesis polymerization50 and Suzuki coupling,51 respectively. FT-IR and 1 HNMR spectra of synthesized P3HT7000-Br with identifying peaks are reported in Figure S1. The 1HNMR spectra were also used to calculate the molecular weight and regioregularity. The FT-IR spectrum of functionalized PEG5000 with boric acid ester (PEG-BE) was also represented in Figure S2. By coupling P3HT7000-Br and PEG-BE, P3HT7000-b-PEG5000 block copolymers resulted (Figure S3). The polydispersity indices (PDI) of purchased PEG5000 (Sigma-Aldrich) (=1.19), synthesized P3HT7000 homopolymers (=1.21) and P3HT7000b-PEG5000 block copolymers (=1.26) were determined with a single unimodal peak reflecting in the size exclusion chromatography (SEC) elutogram (Figure S4). Sample Preparation and Characterization. To prepare all crystalline structures, the solute (homo-PEG5000, homo-P3HT7000, and B

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Macromolecules performed on the final solutions without any filtering or depositing on a substrate. The prepared samples were also characterized by atomic force microscopy (AFM Nanoscope), transmission electron microscopy equipped with electron diffraction (ED) (Philips CM30 TEM), and grazing incidence wide-angle X-ray scattering (GIWAXS) by a CMOS flat panel X-ray detector (C9728DK). The layer spacings or dspacings (d(120) for PEG crystals and d(100) in the hexyl side chains direction and d(020) in π−π stacking direction for P3HT crystals) for the crystalline structures were determined based on Bragg peak positions.52

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RESULTS AND DISCUSSION Figure 1 (top) reports the P3HT-based systems in amyl acetate upon homogenizing the solution by heating (vial with orange solution) and after developing the crystalline structures (vial with brownish red solution). The chemical structures of synthesized P3HT-b-PEG block copolymers are represented in Figure 1 (bottom, left). Furthermore, 1HNMR spectra of synthesized P3HT7000-b-PEG5000 block copolymers are reported in Figure S3. Through assembling the P3HT-based chains into well-designed structures such as half-rang-like crystals, cubic and fibrillar single crystals (Figure 1 (bottom, right)), the color of solution turned from orange to brownish red. Each structure will be scrutinized in the upcoming sections. Scrolled and Flat Crystalline Structures Developed via Unseeded Isothermal Crystallization. In the isothermal crystallization procedure of homo-P3HT7000 chains at Tc = 50 °C, no fibrillar crystals were grown. This could be attributed to too high temperature for the isothermal crystallization without seeding. At lower crystallization temperatures, i.e., 10 and 30 °C, homo-P3HT7000 chains crystallized into the straight and flat nanofibrils with the dimensions of 7−10 nm in the a axis (thickness), 350−400 nm in the b axis (longitude), and 17−18 nm in the c axis (width). These nanofibers were mainly edge-on oriented with the growth planes of (002) in the c axis and (020) in the π−π stacking or b axis detected in ED pattern of Figure 2a. In these nanofibers, the P3HT main backbones and hexyl side chains were parallel with and perpendicular to the substrate, respectively. The width of grown homo-P3HT7000 nanofibers (17−18 nm) was to some extent equal to the extended length of P3HT backbones having the molecular weight of ∼7 kDa.53 It could be inferred that the P3HT backbones were extendedly assembled into these nanofibers, thereby no laminating or folding was detected in the c direction. The only difference between the samples isothermally crystallized at 10 and 30 °C was in their thickness in the a axis. The lower crystallization temperature, the thicker nanofibers; because the lower crystallization temperature provided a somehow larger driving force for the stacking of P3HT backbones in the hexyl side chains direction. When the isothermal crystallization was conducted on the rod−coil P3HT7000-b-PEG5000 block copolymer solutions, the scrolled half-ring-like crystalline structures were developed instead of straight nanofibers (for homo-P3HT7000). Based on ED patterns, the crystallinity and ordering of these scrolled P3HT half-rings were lower than those detected for the flat homo-P3HT7000 nanofibers grown at similar conditions (right inset panel of Figure 2b). In the half-rings of P3HT7000-bPEG5000 block copolymers developed at Tc = 30 °C, only the crystallinity spots of P3HT crystals were observed (Figure 2b). Actually, at this crystallization temperature the PEG5000 blocks were not capable of being crystallized. The width of scrolled half-rings was similar to that of flat homo-P3HT7000 nanofibers, i.e., 17−18 nm. As mentioned previously, in this state the

Figure 2. TEM images accompanied by ED patterns in the right inset panel for (a) flat nanofibers of homo-P3HT7000 isothermally crystallized at 30 °C, (b) scrolled half-rings of P3HT7000-b-PEG5000 block copolymers isothermally crystallized at 30 °C, and (c) scrolled half-rings of P3HT7000-b-PEG5000 block copolymers isothermally crystallized at 10 °C.

P3HT backbones were extendedly arranged in the c direction of crystalline structures. The orientation of P3HT chains in the scrolled half-rings was also edge-on with the growth prisms of (002) and (020). Through decreasing the isothermal crystallization temperature to 10 °C, the PEG blocks also assembled into the lamellar structures on both opposite sides of P3HT scrolled half-rings. Figure 2c depicts TEM image and the corresponding ED pattern of P3HT7000-b-PEG5000 half-rings prepared at Tc = 10 °C. The wider scrolled structures and appearance of (120)PEG spots besides (020)P3HT and (002)P3HT ones were indicative of ordering in the PEG blocks which were previously accumulated on both sides of P3HT half-rings. The total width of scrolled half-rings developed at Tc = 10 °C ranged in 60−65 nm. C

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The scrolling commenced via the isothermal crystallization at Tc = 30 °C, but with a milder curvature. The half-rings prepared at 30 °C did not represent the crystallinity spots for the PEG blocks (Figure 2b). However, even the anisotropic solidification of PEG blocks on the opposite sides of P3HT crystals led to an unbalanced surface stress and, consequently, a mild scrolling. With decreasing the isothermal crystallization temperature, thereby by providing a better opportunity for the PEG crystallization, the curvature in the P3HT half-rings enhanced. It is interesting that, further anisotropic ordering in the PEG arrangement on both sides of half-rings intensified the scrolling. Quite strikingly, thanks to similar surface free energy of the tethered PEG blocks on the opposite sides of the P3HT crystals (i.e., similar material), the unbalanced accumulation of PEG chains on both P3HT crystal surfaces and, consequently, various surface stresses were the driving force for appearing the scrolled crystals. When the PEG blocks were not crystallized and only were solidified, the driving force for scrolling was not that much strong, thereby the degree of curvature was not significant. Through decreasing the crystallization temperature, the PEG blocks were susceptible to develop the lamellar crystalline structures on the opposite surfaces of the P3HT crystal. The asymmetric distribution of PEG lamellae on the opposite sides of the P3HT crystal provided a stronger driving force for scrolling, thereby the degree of curvature increased. In fact, by assembling the PEG blocks into the lamellar structures, the unbalancing in the surface stresses enhanced on the opposite sides of P3HT crystals, hence, the system moved toward further scrolling. The half-rings of P3HT7000-b-PEG5000 block copolymers in both monocrystalline state (only P3HT crystallized) and triplecrystalline state (one P3HT crystalline layer in the middle and two PEG lamellae on the opposite sides) represented an edgeon orientation with (020) and (002) prisms. In more details, at Tc = 30 °C, the P3HT half-ring-like structures showed the spots of (020) and (002) in ED patterns. It was a fingerprint of edgeon oriented P3HT backbones.55−57 No (120)PEG spots were detected at this temperature. On the other side, at Tc = 10 °C, three types of growth prisms were detected, i.e., two pairs of (020)P3HT and (002)P3HT spots as well as two pairs of (120)PEG spots (Figure 2c). These diffraction patterns were assigned to the edge-on oriented P3HT55−57 and flat-on oriented PEG58 chains in the crystalline structures. It was also demonstrated that the crystallinity of PEG coily blocks accumulated on the P3HT curved crystal did not change the extended state of P3HT backbones and also the thickness of half-ring. By

AFM height and phase images of P3HT7000-b-PEG5000 halfrings grown at 10 °C accompanied by the corresponding height profile are represented in Figure 3a−c. In AFM height image,

Figure 3. AFM height image (a), phase image (b), and height profile (c) for scrolled half-rings of P3HT7000-b-PEG5000 block copolymers isothermally developed at 10 °C.

the brighter outer layers were PEG lamellar crystals and the darker inner layer was correlated with the scrolled P3HT crystal. Although the PEG blocks crystallized on opposite surfaces of P3HT half-rings, their crystalline features comprising thicknesses and lateral sizes were dissimilar. As depicted in AFM height profile, in the concave (inner) part, the PEG lamella possessed the thickness and width of ∼15.0 and 18.1 nm, respectively. However, as shown in Figures 3 and 4, the outer PEG lamella was thicker (17.4 nm) and wider (23.1 nm). Different surface stresses on the opposite surfaces of P3HT crystals, originating from diverse levels of crystalline features for PEG lamellae such as thicknesses and lateral sizes led to scrolling, and forming the half-ring-like P3HT structures. Furthermore, the lamellar structure of PEG blocks was discovered by comparing the extended length of PEG5000 (∼27 nm54) with the thickness of PEG flat-on lamellae (15.0 and 17.4 nm).

Figure 4. Schemes of isothermally crystallized homo-P3HT flat nanofiber (left) and P3HT-b-PEG scrolled half-rings in double-crystalline (middle) and monocrystalline (right) states. D

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depicts the explained structure and orientation by the help of a cartoon. AFM height and phase images as well the corresponding height profile of seeded P3HT7000-b-PEG5000 cubic single crystals are represented in Figure 6a−c. The phase

regarding AFM height profiles in the monocrystalline and triple-crystalline states, the width of scrolled P3HT half-ring was ∼17.5 nm and its thickness was 11.0 nm. Previously, Xiong et al.59 scrolled the PEG single crystals using two different types of grafted coily brushes on their opposite sides. On the contrary, in our work the tethered blocks were similar in both surfaces. Therefore, anisotropic accumulation of grafted chains on the opposite sides of P3HT arrangement, and also their subsequent crystallization could in turn lead to the scrolling. Furthermore, herein, the scrolling was found to occur for the conjugated chains such as P3HT, which were more rigid compared to the coily and dielectric PEG ones. The schemes of flat homo-P3HT7000 nanofibers as well as scrolled P3HT7000-b-PEG5000 half-rings with the coily and crystalline PEG precursors are illustrated in Figure 4. The P3HT Regioregular Backbones Grafted with Flaton Orientation on the PEG Simple and Epitaxial Single Crystals. When the homogenized solution of P3HT7000-bPEG5000 block copolymers was seeded by homo-PEG5000 tiny crystals, the cubic PEG single crystals were developed and sandwiched between two layers of grafted regioregular P3HT chains. Figure 5a shows TEM image of seeded P3HT7000-b-

Figure 6. AFM height image (a), phase image (b), and height profile (c) for the cubic P3HT-covered PEG single crystals prepared from P3HT7000-b-PEG5000 block copolymers at 30 °C.

image of cubic PEG single crystals was completely homogeneous and single phase, depicting that whole surface of PEG substrate was covered with the P3HT chains. The overall thickness and lateral size of cubic single crystals ranged from 40.75 to 40.85 nm and from 895 to 910 nm, respectively. Here, we were not able to separately determine the PEG substrate thickness and P3HT brushes height out of the overall thickness acquired from AFM height profile. To circumvent this issue, the channel-wire-channel epitaxial single crystals were developed in the following. To deconvolute the proportion of PEG single crystalline substrate and P3HT orderly grafted chains from the overall thickness, the seeded channel (PEG)/wire (P3HT-covered PEG)/channel (PEG) structures were grown from amyl acetate at 30 °C. The innermost channel or the core of epitaxial structure, whose TEM image and the corresponding ED pattern are depicted in Figure 7a, was homo-PEG5000 single crystal. These cubic single crystals were self-seeded at 40 °C and, consequently, were crystallized at Tc = 30 °C for 8 h. The grown homo-PEG5000 cubic single crystals were injected into homogenized P3HT7000-b-PEG5000 solution which was maintained at 30 °C for 3 min. The crystallization then continued for another 8 h in the presence of the added homo-PEG5000 single crystals, resulting in a wire with a substrate composed of PEG blocks and the grafted P3HT brushes. In fact, addition of homo-PEG5000 single crystals to the growth environment of P3HT7000-b-PEG5000 block copolymers facilitated the attachment of block copolymers from the PEG sides to already prepared cubic single crystals, thereby the unique growth planes, i.e., (120)PEG, were observed for the channel-wire structures (data not shown). A high degree of adaptation was observed between the wire of P3HT7000-b-PEG5000 in the epitaxial single crystals (Figure 7a−c) and the homobrush P3HT-covered PEG single crystals (Figure 5a and Figure 6a−c)

Figure 5. (a) TEM image of seeded P3HT7000-b-PEG5000 cubic single crystals grown at Tc = 30 °C for 24 h in amyl acetate accompanied by the corresponding ED pattern in the right inset panel. (b) Scheme of flat-on regioregular P3HT backbones tethered on the PEG single crystalline substrate.

PEG5000 cubic single crystals grown at Tc = 30 °C for 24 h in amyl acetate. In the corresponding ED pattern (inset of Figure 5a), in addition to four strong (120)PEG prisms, indicating the PEG single crystalline structure, two pairs of weak (020)P3HT and (100)P3HT spots were detected. The appearance of (020)P3HT and (100)P3HT spots for grafted P3HT chains demonstrated the flat-on oriented P3HT backbones on the PEG single crystalline substrate,53 in which the main P3HT backbones and the hexyl side chains were perpendicular to and parallel with the PEG substrate, respectively. In homo-PEG5000 single crystals, only four strong (120) growth planes were detected under electron diffraction (data not shown). Figure 5b E

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substrate thickness from the overall thickness (=40.85 nm), the thickness of tethered P3HT flat-on chains on the PEG substrate was 17.35 nm. This was equivalent to the extended length of P3HT backbones having the molecular weight of ∼7 kDa.53 The bared PEG5000 single crystalline substrate without any tethered chains on the surface possessed the thickness of 11.12 nm, and it reached 6.15 nm after grafting the P3HT backbones. Therefore, the flat-on rigid P3HT backbones acted as the polymer brushes on the PEG substrate and, consequently, exerted a certain osmotic pressure onto it. Furthermore, AFM phase image of epitaxial structure (Figure 7b, right) demonstrated two channels having a common phase (PEG) and a wire in the middle but with a distinct phase, illustrating that the wire was fully covered with the P3HT chains. The dspacing in PEG single crystals was ∼4.65 Å. Moreover, the dspacings of P3HT flat-on backbones in the hexyl side chains, (100), and π−π stacking, (020), directions were ∼19.90 and 4.25 Å, respectively. Flat Fibrillar P3HT-Based Single Crystals via Seeding Method. When the homogenized solutions of P3HT7000-bPEG5000 block copolymers were seeded by homo-P3HT7000 tiny crystals, the fibrillar P3HT single crystals were acquired. To this end, the seeds of homo-P3HT7000 were prepared at the selfseeding temperature of 60 °C in amyl acetate and added to the homogenized P3HT7000-b-PEG5000 solution, which was maintained at 50 °C for 3 min. The crystallization then continued at 50 °C for 24 h to grow the fibrillar P3HT single crystals. The resulted flat fibrillar P3HT7000-b-PEG5000 single crystals are depicted in Figure 8a. In another experiment, the single crystals of homo-P3HT7000 were grown at a similar temperature by Figure 7. Epitaxially grown homo-PEG5000/P3HT7000-b-PEG5000/ homo-PEG5000 single crystals: (a) TEM image and the corresponding ED pattern; (b) AFM height (left) and phase (right) images; (c) AFM height profile.

from the perspective of growth prisms (four strong (120)PEG and two pairs of weak (020)P3HT and (100)P3HT spots) and the overall thickness (40.75−40.85 nm). The orientation of PEG blocks in the cubic single crystals was flat-on. This was proved through four symmetric (120) spots with the d-spacing ∼4.65 Å and a monoclinic unit cell.60 This orientation was similar to that reported previously for the PEG single crystals covered with the conjugated PANI nanorods47−49 and the dielectric polystyrene (PS) and poly(methyl methacrylate) (PMMA) coily brushes.61−66 In a forward step, the channel-wire single crystals were transferred as the seeds to homo-PEG5000 solution, which was homogenized at 70 °C in amyl acetate and kept at 30 °C for 3 min. Afterward, the crystallization continued at the same temperature for 3 h to develop the third channel of epitaxial structure. At the conjunction between the diblock copolymer and homopolymer single crystals, the thickness was found to be confined to the thickness provided with already presented fronts. Therefore, the measurement of thickness at the conjunction of copolymer and homopolymer crystals could reflect an accurate substrate thickness belonging to the block copolymer single crystals.10,61,67,68 The thermodynamic metastable thicknesses of these two types of crystals, due to the energy contribution of P3HT brushes in the diblock sample were not similar, thereby while proceeding the crystallization the exact homo-PEG substrate thickness appeared. As shown in the height profile of Figure 7c, the thickness of single crystalline PEG substrate at conjunction was 6.15 nm. By subtracting the

Figure 8. TEM image of seeded fibrillar single crystals accompanied by the correspondng ED patterns in the right inset panel for (a) P3HT7000-b-PEG5000 and (b) homo-P3HT7000. F

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in plane (IP), respectively. This type of orientation was previously reported in the literature.69−71 Data acquired from ED and GIWAXS patterns highly proved each other, and based on X-ray analyses the d-spacings in the hexyl side chains and π−π stacking directions for homo-P3HT7000 nanofibers were ∼18.40 and 4.00 Å, respectively. The appearance of (200) and (300) spots demonstrated a higher degree of ordering in the analyzed structures. For the scrolled P3HT7000-b-PEG5000 halfrings crystallized at 30 °C (monocrystalline), a similar 2D GIWAXS pattern was reached, but with a lower degree of ordering. Because the finger prints of highly ordering, i.e., (200) and (300) planes disappeared (Figure 10(b)). For the scrolled P3HT7000-b-PEG5000 half-rings prepared at 10 °C with PEG lamellae on the opposite sides of P3HTs (double-crystalline), in addition to (100)OOP and (020)IP planes, (120) spots were detectable (Figure 10c). The values for d(120), d(100)OOP, and d(020)IP were 4.66, 18.45, and 4.08 Å, respectively. The GIWAXS patterns for the cubic P3HT7000-b-PEG5000 (Figure 10d) and the epitaxial homo-PEG 5000 /P3HT 7000 -b-PEG 5000 /homoPEG5000 (Figure 10e) single crystals were similar, indicating that the subsequent channels were developed with the common growth planes. In these structures, both PEG and P3HT blocks were flat-on oriented in the single crystalline substrate and tethered brush roles, respectively. The (120) planes as well as (100) (hexyl side chains), (020) (π−π stacking), and (002) (longitude of P3HT backbones) demonstrated the crystallization and ordering of PEG and P3HT chains. The d-spacing in PEG single crystals was ∼4.65 Å, and in ordered P3HT backbones was ∼19.91 and 4.24 Å. As shown in Figures 10(f) and (g) for seeded firillar homo-P3HT7000 and P3HT7000-bPEG5000 single crystals, the designation of (100)OOP and (020)IP resembled those detected for unseeded homo-P3HT 7000 nanofibers, but with stronger intensities. This was originated from a larger ordered structure of the seeded single crystals compared with the unseeded nanofibers, but both with the edge-on orientation. For homo-P3HT7000 and P3HT7000-bPEG5000 single crystals, the values of (100)OOP and (020)IP were ∼16.80 and 3.64 Å, respectively. The P3HT chains demonstrated the most absorbance and ordered structures in homo-P3HT7000 and P3HT7000-b-PEG5000 fibrillar single crystals. The thicknesses and lengths of these fibrillar highly crystalline single crystals ranged from 20 to 22 nm and from 60 to 63 μm, respectively. As mentioned before, homo-P3HT7000 and P3HT7000-b-PEG5000 fibrillar single crystals were different from the perspective of crystal width in the c direction or the longitude of P3HT backbones (360 versus 40 nm). The UV−vis spectra of homo-P3HT7000 single crystals illustrated a bit higher intensity and also somewhat of a redshifting compared to P3HT7000-b-PEG5000 ones (Figure 11). It could originate from more ordered structures for P3HT backbones. The peaks from left were entitled A0−2, A0−1, and A0−0, respectively. As shown in Figure 11, for homo-P3HT7000 (P3HT7000-b-PEG5000) fibrillar single crystals, A0−2, A0−1, and A0−0 peaks appeared at 516 (513), 572 (564), and 640 (632) nm, respectively. On the other hand, the peaks of unseeded homo-P3HT7000 nanofibers prepared with an isothermal crystallization were blue-shifted (A0−2 = 516 nm, A0−1 = 556 nm, and A0−0 = 594 nm) with significant lower intensities compared to the corresponding single crystals (Figure 11). This was originated from their smaller assemblies (a = 7−10 nm, b = 350−400 nm, and c = 17−18 nm) as well as their lower structural ordering compared with the corresponding homoP3HT7000 single crystals. The d-spacings in the hexyl side chains

employing the self-seeding protocol (Figure 8b). The thicknesses and lengths of homo-P3HT7000 and P3HT7000-bPEG5000 fibrillar single crystals resembled each other, ranging from 20 to 22 nm and from 60 to 63 μm, respectively. In a strong contrast, their width or dimension in the c axis or longitude of P3HT backbones were significantly different. The width of homo-P3HT7000 and P3HT7000-b-PEG5000 fibrillar single crystals were ∼360 and 40 nm, respectively. By consideration of the extended length of P3HT7000 backbones (∼17.2 nm53), the number of laminated P3HT backbones in the c axis of homo-P3HT7000 and P3HT7000-b-PEG5000 fibrillar single crystals were determined to be 21 and 2, respectively. It was very interesting that in contrast to the homopolymer single crystals, in the block copolymer single crystals, only two P3HT backbones were allowed to be laminated on each other in the c direction (Figure 9). It could be supposed that the P3HT

Figure 9. Scheme of seeded fibrillar P3HT-based block copolymer single crystals in which two backbones are laminated and the PEG coily blocks are accumulated in the c axis or the backbone longitude.

backbones were not capable of being laminated from the coily block sides. Therefore, only two P3HT backbones were able to be laminated on each other through ejecting their end coily blocks toward outside of grown single crystal. Both homoP3HT7000 and P3HT7000-b-PEG5000 single crystals represented the strong (002) and (020) spots, proving that the P3HT backbones had an edge-on orientation with the hexyl side chains perpendicular to the substrate. Furthermore, no trace of crystallization was detected for the PEG coily blocks in P3HT7000-b-PEG5000 single crystals. It could be inferred that the PEG dielectric coily blocks were accumulated on both opposite sides of P3HT fibrillar single crystals in the c axis without having an opportunity for crystallization. This was illustrated in the scheme of Figure 9 with identifying precursors. An interesting point to be mentioned is that, the seeded crystalline P3HT structures did not demonstrate any scrolling or curvature like the corresponding unseeded crystals prepared from P3HT7000-b-PEG5000 block copolymers. In fact, the seeding procedure dictated a routine crystallization path for the P3HT backbones, thereby prevented them from assembling in a scrolled manner. The X-ray and Absorbance Properties of Distinct Scrolled/Flat Crystalline Structures. The 2D GIWAXS plots of Figure 10 for seeded and unseeded crystalline structures were recorded to verify the structural and orientational characteristics. Considering Figure 10a, the flat homoP3HT7000 nanofibers with edge-on oriented P3HT backbones represented (100) and (020) spots in out of plane (OOP) and G

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Figure 10. 2D GIWAXS plots of (a) flat nanofibers of homo-P3HT7000 isothermally crystallized at 30 °C; (b) scrolled half-rings of P3HT7000-bPEG5000 block copolymers isothermally crystallized at 30 °C; (c) scrolled half-rings of P3HT7000-b-PEG5000 block copolymers isothermally crystallized at 10 °C; (d) cubic P3HT-covered PEG single crystals prepared from P3HT7000-b-PEG5000 block copolymers at 30 °C; (e) epitaxially grown homo-PEG5000/P3HT7000-b-PEG5000/homo-PEG5000 single crystals developed at 30 °C; (f) seeded fibrillar homo-P3HT7000 single crystals prepared at 50 °C; (g) seeded fibrillar P3HT7000-b-PEG5000 single crystals prepared at 50 °C.

and π−π stacking directions for homo-P3HT7000 nanofibers were ∼18.40 and 3.99 Å and for homo-P3HT7000 single crystals were ∼16.81 and 3.64 Å, respectively. The half-ring-like P3HT crystalline structures developed at Tc = 10 and 30 °C represented the similar spectra from viewpoint of peak intensity and peak position. The A0−2, A0−1, and A0−0 peaks appeared at 501, 548, and 584 nm, respectively. The respective UV−vis spectra are reported in Figure 11. It could be concluded that the conformation and arrangement of PEG blocks on the opposite sides of half-ring-like P3HT crystals did not affect their absorbance properties. The most blue-shifted and the least intensified A0−2, A0−1, and A0−0 peaks were detected for the samples in which the P3HT backbones were grafted as the conductive brushes on the PEG single

crystalline cubic substrate. The lower portion and crowd of tethered P3HT chains on the substrate, the lower absorbance in UV−vis spectra. In more details, A0−2, A0−1, and A0−0 peaked at 496, 541, and 577 nm for the nonepitaxial P3HT7000-b-PEG5000 cubic single crystals and peaked at 493, 538, and 575 nm for the epitaxial homo-PEG5000/P3HT7000-b-PEG5000/homo-PEG5000 single crystals (Figure 11). As a point to be made, the P3HT extended chains as the conjugated polymer and rigid brushes were capable of assembling in a reasonable state and showing their conductivity and absorbance features. However, this assembling was not comparable with their stacking in the nanofibers and more especially in the single crystals. H

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Nonequilibrium to Near Equilibrium. Macromolecules 2006, 39, 324−329. (3) Ma, Z.; Zhang, G.; Zhai, X.; Jin, L.; Tang, X.; Yang, M.; Zheng, P.; Wang, W. Fractal Crystal Growth of Poly (ethylene oxide) Crystals from Its Amorphous Monolayers. Polymer 2008, 49, 1629−1634. (4) Zhang, G.; Cao, Y.; Jin, L.; Zheng, P.; Van Horn, R. M.; Lotz, B.; Cheng, S. Z. D.; Wang, W. Crystal Growth Pattern Changes In Low Molecular Weight Poly (ethylene oxide) Ultrathin Films. Polymer 2011, 52, 1133−1140. (5) Agbolaghi, S.; Abbasi, F.; Abbaspoor, S. Epitaxial Single Crystal Surface Patterning and Study of Physical and Chemical Environmental Effects on Crystal Growth. Colloid Polym. Sci. 2014, 292, 1375−1383. (6) Keller, A.; Cheng, S. Z. D. The Role of Metastability In Polymer Phase Transitions. Polymer 1998, 39, 4461−4487. (7) Cheng, S. Z. D.; Keller, A. The Role of Metastable States In Polymer Phase Transitions: Concepts, Principles, and Experimental Observations. Annu. Rev. Mater. Sci. 1998, 28, 533−562. (8) Li, B.; Wang, B. B.; Ferrier, R. C. M.; Li, C. Y. Programmable Nanoparticle Assembly Via Polymer Single Crystals. Macromolecules 2009, 42, 9394−9399. (9) Dong, B.; Wang, W. D.; Miller, D. L.; Li, C. Y. Polymer-SingleCrystal@Nanoparticle Nanosandwich for Surface Enhanced Raman spectroscopy. J. Mater. Chem. 2012, 22, 15526−15529. (10) Chen, W. Y.; Li, C. Y.; Zheng, J. X.; Huang, P.; Zhu, L.; Ge, Q.; Quirk, R. P.; Lotz, B.; Deng, L.; Wu, C.; Thomas, E. L.; Cheng, S. Z. D. Chemically Shielded Poly(ethylene oxide) Single Crystal Growth and Construction of Channel-Wire Arrays with Chemical and Geometric Recognitions on A Submicrometer Scale. Macromolecules 2004, 37, 5292−5299. (11) Li, B.; Li, L. Y.; Wang, B. B.; Li, C. Y. Alternating Patterns on Single-Walled Carbon Nanotubes. Nat. Nanotechnol. 2009, 4, 358− 362. (12) Li, C. Y. Polymer Single Crystal Meets Nanoparticles. J. Polym. Sci., Part B: Polym. Phys. 2009, 47, 2436−2440. (13) Chen, W. Y.; Zheng, J. X.; Cheng, S. Z. D.; Li, C. Y.; Huang, P.; Zhu, L.; Xiong, H. M.; Ge, Q.; Guo, Y.; Quirk, R. P.; Lotz, B.; Deng, L. F.; Wu, C.; Thomas, E. L. Onset of Tethered Chain Overcrowding. Phys. Rev. Lett. 2004, 93, 028301. (14) Dong, B.; Miller, D. L.; Li, C. Y. Polymer Single Crystal As Magnetically Recoverable Support For Nanocatalysts. J. Phys. Chem. Lett. 2012, 3, 1346−1350. (15) Li, B.; Li, C. Y. Immobilizing Au Nanoparticles with Polymer Single Crystals, Patterning and Asymmetric Functionalization. J. Am. Chem. Soc. 2007, 129, 12−13. (16) Wang, B. B.; Li, B.; Dong, B.; Zhao, B.; Li, C. Y. Homo- and Hetero-Particle Clusters Formed by Janus Nanoparticles with Bicompartment Polymer Brushes. Macromolecules 2010, 43, 9234− 9238. (17) Fujiki, Y.; Tokunaga, N.; Shinkai, S.; Sada, K. Anisotropic Decoration of Gold Nanoparticles Onto Specific Crystal Faces of Organic Single Crystals. Angew. Chem. 2006, 118, 4882−4885. (18) Minemawari, H.; Yamada, T.; Matsui, H.; Tsutsumi, J.; Haas, S.; Chiba, R.; Kumai, R.; Hasegawa, T. Inkjet Printing of Single-Crystal Films. Nature 2011, 475, 364−367. (19) Kim, D. H.; Han, J. T.; Park, Y. D.; Jang, Y.; Cho, J. H.; Hwang, M.; Cho, K. Single-Crystal Polythiophene Microwires Grown by SelfAssembly. Adv. Mater. 2006, 18, 719−723. (20) Jiang, X.; Liu, X.; Liao, Q.; Wang, X.; Yan, D. D.; Huo, H.; Li, L.; Zhou, J. J. Probing Interfacial Properties Using a Poly(ethylene oxide) Single Crystal. Soft Matter 2014, 10, 3238−3244. (21) Di Bonito, P.; Petrone, L.; Casini, G.; Francolini, I.; Ammendolia, M. G.; Accardi, L.; Piozzi, A.; D’Ilario, L.; Martinelli, A. Amino-Functionalized Poly (L-lactide) Lamellar Single Crystals As a Valuable Substrate for Delivery of hPV16-e7 Tumor Antigen In Vaccine Development. Int. J. Nanomed. 2015, 10, 3447−3458. (22) D’Ilario, L.; Francolini, I.; Martinelli, A.; Piozzi, A. Dipyridamole-Loaded Poly(L-lactide) Single Crystals As Drug Delivery Systems. Macromol. Rapid Commun. 2007, 28, 1900−1904.

Figure 11. UV−vis spectra of various samples prepared from P3HTbased polymers.

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CONCLUSIONS Herein, the flat and scrolled P3HT-based crystalline structures were developed by seeding and isothermal crystallization methodologies. The unbalanced accumulation and also in a further step, the lamellar crystallization of PEG dielectric blocks in unseeded systems led to scrolled P3HT half-rings with extended and edge-on backbones. Moreover, seeding of P3HT7000-b-PEG5000 homogenized solutions with homoPEG 5000 and homo-P3HT7000 tiny crystals resulted in sandwiched cubic P3HT-covered PEG single crystals and fibrillar P3HT single crystals, respectively. The thickness of PEG substrate and extended flat-on P3HT tethered chains with (020) and (100) prisms were verified by the channel (PEG)/ wire (P3HT-covered PEG)/channel (PEG) single crystals. Furthermore, the characteristics of homo-P3HT7000 and P3HT7000-b-PEG5000 fibrillar single crystals were investigated from the perspective of number of backbone lamination (21 versus 2) in their width and orientation (both edge-on with (020) and (002) fronts).

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.macromol.6b02295. FT-IR and 1H NMR spectra, SEC plots, and scheme of distinct protocols to prepare the P3HT configurations (PDF)

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AUTHOR INFORMATION

Corresponding Author

*(F.A.) E-mail: [email protected]. ORCID

Samira Agbolaghi: 0000-0003-0461-3317 Notes

The authors declare no competing financial interest.

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REFERENCES

(1) Lotz, B.; Kovacs, A. J.; Bassett, G. A.; Keller, A. Properties of Copolymers Composed of One Poly-ethylene-oxide and One Polystyrene Block. Kolloid Z. Z. Polym. 1966, 209, 115−128. (2) Zhai, X.; Wang, W.; Zhang, G.; He, B. Crystal Pattern Formation and Transitions of PEO Monolayers on Solid Substrates from I

DOI: 10.1021/acs.macromol.6b02295 Macromolecules XXXX, XXX, XXX−XXX

Article

Macromolecules (23) Petrone, L.; Ammendolia, M. G.; Cesolini, A.; Caimi, S.; Superti, F.; Giorgi, C.; Di Bonito, P. Recombinant HPV16 E7 Assembled Into Particlesinduces an Immune Response and Specific Tumour Protection Administered without Adjuvantin an Animal Model. J. Transl. Med. 2011, 9, 69. (24) De Boer, R.; Gershenson, M.; Morpurgo, A.; Podzorov, V. Organic Single-Crystal Field-Effect Transistors. Phys. Status Solidi (a) 2004, 201, 1302−1331. (25) Sundar, V. C.; Zaumseil, J.; Podzorov, V.; Menard, E.; Willett, R. L.; Someya, T.; Gershenson, M. E.; Rogers, J. A. Elastomeric Transistor Stamps: Reversible Probing of Charge Transport In Organic Crystals. Science 2004, 303, 1644−1646. (26) Briseno, A. L.; Aizenberg, J.; Han, Y. J.; Penkala, R. A.; Moon, H.; Lovinger, A. J.; Kloc, C.; Bao, Z. Patterned Growth of Large Oriented Organic Semiconductor Single Crystals on Self-Assembled Monolayer Templates. J. Am. Chem. Soc. 2005, 127, 12164−12165. (27) Moon, H.; Zeis, R.; Borkent, E. J.; Besnard, C.; Lovinger, A. J.; Siegrist, T.; Kloc, C.; Bao, Z. Synthesis, Crystal Structure, and Transistor Performance of Tetracene Derivatives. J. Am. Chem. Soc. 2004, 126, 15322−15323. (28) Podzorov, V.; Menard, E.; Borissov, A.; Kiryukhin, V.; Rogers, J.; Gershenson, M. Intrinsic Charge Transport on The Surface of Organic Semiconductors. Phys. Rev. Lett. 2004, 93, 086602. (29) Zeis, R.; Besnard, C.; Siegrist, T.; Schlockermann, C.; Chi, X.; Kloc, C. Field Effect Studies on Rubrene and Impurities of Rubrene. Chem. Mater. 2006, 18, 244−248. (30) Berson, S.; De Bettignies, R.; Bailly, S.; Guillerez, S. Poly (3hexylthiophene) Fibers for Photovoltaic Applications. Adv. Funct. Mater. 2007, 17, 1377−1384. (31) Rotzoll, R.; Mohapatra, S.; Olariu, V.; Wenz, R.; Grigas, M.; Dimmler, K.; Shchekin, O.; Dodabalapur, A. Radio Frequency Rectifiers Based on Organic Thin-Film Transistors. Appl. Phys. Lett. 2006, 88, 123502−123502. (32) Tseng, R. J.; Huang, J.; Ouyang, J.; Kaner, R. B.; Yang, Y. Polyaniline Nanofiber/Gold Nanoparticle Nonvolatile Memory. Nano Lett. 2005, 5, 1077−1080. (33) Hernandez, S. C.; Chaudhuri, D.; Chen, W.; Myung, N. V.; Mulchandani, A. Single Polypyrrole Nanowire Ammonia Gas Sensor. Electroanalysis 2007, 19, 2125−2130. (34) Agbolaghi, S.; Abbasi, F.; Gheybi, H. High Efficient and Stabilized Photovoltaics Via Morphology Manipulating In Active layer by Rod-Coil Block Copolymers Comprising Different Hydrophilic To Hydrophobic Dielectric Blocks. Eur. Polym. J. 2016, 84, 465−480. (35) De Vusser, S.; Steudel, S.; Myny, K.; Genoe, J.; Heremans, P. Integrated Shadow Mask Method for Patterning Small Molecule Organic Semiconductors. Appl. Phys. Lett. 2006, 88, 103501. (36) Dickey, K. C.; Subramanian, S.; Anthony, J. E.; Han, L. H.; Chen, S.; Loo, Y. L. Large-Area Patterning of A Solution-Processable Organic Semiconductor To Reduce Parasitic Leakage and Off Currents In Thin-Film Transistors. Appl. Phys. Lett. 2007, 90, 244103. (37) Surin, M.; Leclere, P.; Lazzaroni, R.; Yuen, J.; Wang, G.; Moses, D.; Heeger, A.; Cho, S.; Lee, K. Relationship Between The Microscopic Morphology and The Charge Transport Properties In Poly (3-hexylthiophene) Field-Effect Transistors. J. Appl. Phys. 2006, 100, 033712. (38) Yang, X.; Loos, J.; Veenstra, S. C.; Verhees, W. J.; Wienk, M. M.; Kroon, J. M.; Michels, M. A.; Janssen, R. A. Nanoscale Morphology of High-Performance Polymer Solar Cells. Nano Lett. 2005, 5, 579−583. (39) Savenije, T. J.; Kroeze, J. E.; Yang, X.; Loos, J. The Formation of Crystalline P3HT Fibrils Upon Annealing of A PCBM:P3HT Bulk Heterojunction. Thin Solid Films 2006, 511-512, 2−6. (40) Salleo, A. Charge Transport In Polymeric Transistors. Mater. Today 2007, 10, 38−45. (41) Yang, H.; Shin, T. J.; Yang, L.; Cho, K.; Ryu, C. Y.; Bao, Z. Effect of Mesoscale Crystalline Structure on The Field-Effect Mobility of Regioregular Poly (3-hexyl thiophene) In Thin-Film Transistors. Adv. Funct. Mater. 2005, 15, 671−676. (42) Jimison, L. H.; Toney, M. F.; McCulloch, I.; Heeney, M.; Salleo, A. Charge-Transport Anisotropy Due to Grain Boundaries in

Directionally Crystallized Thin Films of Regioregular Poly (3hexylthiophene). Adv. Mater. 2009, 21, 1568−1572. (43) Briseno, A. L.; Mannsfeld, S. C.; Jenekhe, S. A.; Bao, Z.; Xia, Y. Introducing Organic Nanowire Transistors. Mater. Today 2008, 11, 38−47. (44) Samitsu, S.; Shimomura, T.; Heike, S.; Hashizume, T.; Ito, K. Effective Production of Poly (3-alkylthiophene) Nanofibers by Means of Whisker Method Using Anisole Solvent: Structural, Optical, and Electrical Properties. Macromolecules 2008, 41, 8000−8010. (45) Xin, H.; Kim, F. S.; Jenekhe, S. A. Highly Efficient Solar Cells Based on Poly (3-butylthiophene) Nanowires. J. Am. Chem. Soc. 2008, 130, 5424−5425. (46) Wang, Y.; Chen, J.; Li, S.; Li, L.; Su, Q.; Wang, J.; Yang, X. Semiconductor−Insulator− Semiconductor Sandwiched Lozenge Crystals of Poly (3-butylthiophene)-block-polyethylene Copolymer. Macromolecules 2011, 44, 1737−1741. (47) Nazari, M.; Agbolaghi, S.; Abbaspoor, S.; Gheybi, H.; Abbasi, F. Arrangement of Conductive Rod Nanobrushes via Conductive− Dielectric−Conductive Sandwiched Single Crystals of Poly (ethylene glycol) and Polyaniline Block Copolymers. Macromolecules 2015, 48, 8947−57. (48) Agbolaghi, S.; Nazari, M.; Abbaspoor, S.; Gheybi, H.; Abbasi, F. Micro/Nano Conductive-Dielectric Channels Designed by Poly (ethylene glycol) Single Crystals Covered by Polyaniline Nanofibers. Polymer 2016, 92, 264−272. (49) Agbolaghi, S.; Nazari, M.; Abbaspoor, S.; Gheybi, H.; Abbasi, F. Characterization of Novel Extremely Extended Regime In Conductive Rod-Like Polyaniline Nanobrush-Covered Poly (ethylene glycol) Single Crystals. Eur. Polym. J. 2016, 82, 196−207. (50) Lohwasser, R. H.; Thelakkat, M. Toward Perfect Control of End Groups and Polydispersity In Poly (3-hexylthiophene) Via Catalyst Transfer Polymerization. Macromolecules 2011, 44, 3388−3397. (51) Li, F.; Shi, Y.; Yuan, K.; Chen, Y. Fine Dispersion and SelfAssembly of ZnO Nanoparticles Driven by P3HT-b-PEO Diblocks for Improvement of Hybrid Solar Cells Performance. New J. Chem. 2013, 37, 195−203. (52) Kim, J. Y.; Frisbie, C. D. Correlation of Phase Behavior and Charge Transport In Conjugated Polymer/Fullerene Blends. J. Phys. Chem. C 2008, 112, 17726−17736. (53) Rahimi, K.; Botiz, I.; Stingelin, N.; Kayunkid, N.; Sommer, M.; Koch, F. P.; Nguyen, H.; Coulembier, O.; Dubois, P.; Brinkmann, M.; Reiter, G. Controllable Processes for Generating Large Single Crystals of Poly (3-hexylthiophene). Angew. Chem., Int. Ed. 2012, 51, 11131− 11135. (54) Cauda, V.; Argyo, C. H.; Bein, T. H. Impact of Different PEGylation Patterns on The Long-Term Bio-Stability of Colloidal Mesoporous Silica Nanoparticles. J. Mater. Chem. 2010, 20, 8693− 8699. (55) Salim, T.; Lek, J. Y.; Bräuer, B.; Fichou, D.; Lam, Y. M. Polymer Nanofibers: Preserving Nanomorphology in Ternary Blend Organic Photovoltaics. Phys. Chem. Chem. Phys. 2014, 16, 23829−23836. (56) Zhao, Y.; Shao, S.; Xie, Z.; Geng, Y.; Wang, L. Effect of Poly (3hexylthiophene) Nanofibrils on Charge Separation and Transport in Polymer Bulk Heterojunction Photovoltaic Cells. J. Phys. Chem. C 2009, 113, 17235−17239. (57) Oosterbaan, W. D.; Vrindts, V.; Berson, S.; Guillerez, S.; Douhéret, O.; Ruttens, B.; D’Haen, J.; Adriaensens, P.; Manca, J.; Lutsen, L.; Vanderzande, D. Efficient Formation, Isolation and Characterization of Poly (3-alkylthiophene) Nanofibres: Probing Order As A Function of Side-Chain Length. J. Mater. Chem. 2009, 19, 5424−5435. (58) Yang, P.; Han, Y. Crystal Growth Transition from Flat-on to Edge-on Induced by Solvent Evaporation in Ultrathin Films of Polystyrene-b-poly (ethylene oxide). Langmuir 2009, 25, 9960−9968. (59) Xiong, H.; Chen, C. K.; Lee, K.; Van Horn, R. M.; Liu, Z.; Ren, B.; Quirk, R. P.; Thomas, E. L.; Lotz, B.; Ho, R. M.; Zhang, W. B.; Cheng, S. Z. D. Scrolled polymer Single Crystals Driven by Unbalanced Surface Stresses: Rational Design and Experimental Evidence. Macromolecules 2011, 44, 7758−7766. J

DOI: 10.1021/acs.macromol.6b02295 Macromolecules XXXX, XXX, XXX−XXX

Article

Macromolecules (60) Van Horn, R. M. Tethered Polymer Chains on Single Crystal Surfaces. Ph.D. Dissertation. University of Akron: 2009. (61) Abbaspoor, S.; Abbasi, F.; Agbolaghi, S. A Novel Approach to Prepare Polymer Mixed-Brushes Via Single Crystal Surface Patterning. RSC Adv. 2014, 4, 17071−17082. (62) Agbolaghi, S.; Alizadeh-Osgouei, M.; Abbaspoor, S.; Abbasi, F. Self-Assembling Nano Mixed-Brushes Having Co-Continuous Surface Morphology by Melt Growing Single Crystals and Comparison with Solution Patterned Leopard-Skin Surface Morphology. RSC Adv. 2015, 5, 1538−1548. (63) Agbolaghi, S.; Abbasi, F.; Abbaspoor, S.; Alizadeh-Osgouei, M. Self-Designed Surfaces Via Single-Co-Crystallization of Homopolymer and Diblock Copolymers In Various Growth Conditions. Eur. Polym. J. 2015, 66, 108−118. (64) Alizadeh-Osgouei, M.; Agbolaghi, S.; Abbaspoor, S.; Abbasi, F. A Subtle Insight Into Nano-Convergence of Substrate Thickness in MeltGrown Single-Co-Crystals. Colloid Polym. Sci. 2016, 294, 869−878. (65) Agbolaghi, S.; Abbaspoor, S.; Abbasi, F. Synthesis of Polymer Nano-Brushes by Self-Seeding Method and Study of Various Morphologies by AFM. Int. Nano Lett. 2016, 6, 11−19. (66) Agbolaghi, S.; Abbaspoor, S.; Abbasi, F. Detection of Polymer Brushes Developed Via Single Crystal Growth. Int. J. Nanosci. Nanotechnol. 2016, 12, 79−90. (67) Chen, Y. Single Crystal Engineering of Amorphous-Crystalline Block Copolymers Crystallization, Morphology and Applications. Ph.D. Dissertation. University of Akron: 2005. (68) Zheng, J. X.; Xiong, H.; Chen, W. Y.; Lee, K.; Van Horn, R. M.; Quirk, R. P.; Lotz, B.; Thomas, E. L.; Shi, A. C.; Cheng, S. Z. D. Onsets of Tethered Chain Overcrowding and Highly Stretched Brush Regime Via Crystalline-Amorphous Diblock Copolymers. Macromolecules 2006, 39, 641−650. (69) Agostinelli, T.; Lilliu, S.; Labram, J. G.; Campoy-Quiles, M.; Hampton, M.; Pires, E.; Rawle, J.; Bikondoa, O.; Bradley, D. D. C.; Anthopoulos, T. D.; Nelson, J.; Macdonald, J. E. Real-Time Investigation of Crystallization and Phase-Segregation Dynamics in P3HT: PCBM Solar Cells During Thermal Annealing. Adv. Funct. Mater. 2011, 21, 1701−1708. (70) Liao, H. C.; Tsao, C. S.; Lin, T. H.; Chuang, C. M.; Chen, C. Y.; Jeng, U. S.; Su, C. H.; Chen, Y. F.; Su, W. F. Quantitative nanoorganized structural evolution for a high efficiency bulk heterojunction polymer solar cell. J. Am. Chem. Soc. 2011, 133, 13064−13073. (71) Balderrama, V. S.; Estrada, M.; Viterisi, A.; Formentin, P.; Pallarés, J.; Ferré-Borrull, J.; Palomares, E.; Marsal, L. F. Correlation between P3HT inter-chain structure and J sc of P3HT: PC [70] BM blends for solar cells. Microelectron. Reliab. 2013, 53, 560−564.

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